High-frequency multiplier system



Jan. 6, 1948. s. E.- PIHL HIGH-FREQUENCY MULTIPLIER sr smu Filed Oct.31, 1945 FIG.

INVENTDR G.E.PIHL

FIG. 3

ATTORNEY that are biased to operate at or past the Patented Jan. 6 1948George E. Pihl, Boston, Western Union Telegra Mass., assignor to The 'phCompany, New York,

N. Y., a corporation of New York Application October 31, 1945, SerialNo. 625,855

'1 Claims. (01. 172-281) This invention relates generally to highfrequency harmonic larly to multipliers for producing ultra-highfrequencies and microwaves.

Various types of frequency multipliers, and particularly frequencydoublers, for relatively low frequency currents have long been known.Such multipliers commonly involve an input transformer having a primarywinding on which is impressed an original frequency, the transformerhaving its secondary winding associated with a rectifier circuit toprovide full wave rectification of the original wave impressed on theinput winding. The rectified current includes an alternating currentcomponent of twice the frequency of the original wave, and by means of asecond transformer or other circuit elements an alter-' nating currentcomponent is obtained which is twice the frequency of the original wave.Other known arrangements involve applying two or more alternatingcurrents, differing in phase from .each other, to rectifier andtransformer circuits to obtain the second harmonic of the input frepriorarrangements, of

quency. None of these however, is suit'able for harmonic generatorsultra-high frequencies and microwaves.

In high frequency systems it has been proposed heretofore to employharmonic generators, such as frequency doublers, involving electrontubes knee of their saturation curves. These require complicatedelectronic structures and circuit arrangements, with attendant close andcritical spacing of the electron elements, and are subject to variationwhich prevents them from having a desired stability of performance, andthey involve serious adjustment and maintenance problems.

One of the objects of the present invention is generators, and moreparticu a wave length of 12 cm.

illustrative embodiment thereof, taken in connection with theaccompanying drawings in which:

Fig. 1 shows a microwave frequency doubler constructed in accordancewith the principles of the invention;

Fig. 2 shows wave form curves of certain standing wave components ofvoltage and current produced in the operation of the device of Fig. 1;and

Fig. 3 shows similar wave form curves employed in explaining theoperation of a modified form of the device.

Referring to the drawings, there is shown a coaxial line structurecomprising a metallic tube ill, of brass, copper or other suitablematerial, which encloses a central conductor ll, these elements beingconnected to, or comprising a portion of, a coaxial system that providesan input source of alternating current having, for example, a frequencyof 2500 mc., corresponding to The central conductor Il may be either asolid wire or a small hollow tube, and is centrally supported within theouter tube l 0 in knownmanner, as' by means of spacers or washers ofpolystyrene, isolantite. or other suitable low-loss insulating material.Any other suitable supporting means may be' employed so long as it doesnot interfere with the desired tuning and resonant characteristics ofthe tube structure. In the embodiment illustrated in the drawing theright hand end of the tube I0 is closed by a solid plate Illa of brass,copper or other material, although as hereinafter pointed out the tubemay be openat this end.

to provide a harmonic generator for very high frequencies, in whichvarious of the structural and operating disadvantages of devicesheretofore proposed'are obviate Another object is a harmonic generatorof ultrahigh frequencies and microwaves, which is simple in structureand is extremely stable in operation.

An additional object is a harmonic generator of the character describedin which no electronic devices or complicated arrangements are required.

A further object is an improved harmonic generator which is especiallyadapted for use with coaxial systems for, generating extremely shortelectromagnetic waves, for example, having wave lengths of the 'order ofa few centimeters.

' Other objects and advantages will be apparent from the followingdetailed description of one Secured to and in communication with thetube I0 are two bent coaxial sections I2 and I4 within which arecentrally positioned conductors l5 and Hi, the input ends of whichareelectrically connected at points a and b to the conductor H, theiroutput ends being connected to crystal rectifiers i8 centrallypositioned within the tubes l2 and H, the distance between therectifiers preferably being as short as possible. The rectifiers arepoled with respect to each other, as indicated in the drawing, and arerigidly supported in position within the tubes 12 and M in any suitablemanner, as by mounting them within washers or blocks of polystyrene orother suitable means. v

The distance between the points a and b and, consequently, that portionof the tube l 0 between these points, is such that for an input wavehaving av given wave length A, the spacing between them; 'nninte nv-"*"A I the stored energy ration and proportions of chamber in tube Itwill correspond to 2 The term standing wave hereinafter referred to isto be understood as, including a traveling energy component which issmall compared to That portion of the tube between the point D and theclosed end Illa. thereof has a length which corresponds to of thefundamental wave, whereby the voltage or any odd one-half wave length ofthe fundamental wave. This will in general minimize the crystal currentat the fundamental frequency thereby to obviate possibility of injury tothe crystals. Connected to the conductors l5 and It, at a point e whichis midway tal rectifiers i8, is a centrally positioned conductor 20, thelower end of which forms a loop 20a end of a cylindrical resonant wavechamber 22, of brass or other suitable material, for exciting thechamber. The conductor 20 is centrally positioned within a length oftubing 23 thereby forming a coupler that extends from the adjoining endsof the tubular sections 5 be used, and the configuration of between thecrys- I2 and it through an end wall of the chamber 22. The length of theconducting path between each of the crystal rectifiers i8 andtheexciting loop at the output end of conductor 20 preferably correspondsto or any odd one-eighth wave length of the fundamental wave abovereferred to, thereby to provide maximum transfer of energy to thetransmitting loop for exciting the chamber 22, and also to minimizecrystal current at the frequency of the second harmonic.

Positioned within the lower, or output, end of the resonant chamber 22is a conductor 26 having an end 26a that forms a receiving or pickuploop for the waves set up within the resonant chamber. The conductor 26is centrally positioned within a tube 21, and in the coaxial circuitformed by the elements 26 and 21 there is induced an alternating currenthaving a frequency that corresponds to the resonant frequency of thechamber 22;

In the illustrative embodiment the positions of the exciting and pickuploops, and the configu- 22, cause the chamber to be resonant at the wavelength of The arrangement thus operates to select and retransmit wavelengths which are one-half that of the fundamental wave length of theener y input to the resonant section i0, I l. Other forms of exciting"and; pickup loops, or antennae, may the resonant chamber will varyaccordingly, depending upon the rediation characteristic and pattern ofthe particular transmitting and receiving antennae employed. While theresonant chamber illustrated serves'to select and retransmit the secondharmonic of the fundamental wave length, it may be designed to selectand retransmit various other even-numbered harmonics thereof, althoughthe second harmonic is predominant and thus the greatest transfer ofenergy to the line 26, 2'! will occur at such frequency. The lineardimension of the resonant section between the points a and b, and thatof the section between the point b and the right hand end of the tube10, will be different for operation at different input frequencies, andto facilitate this adjustable trombone sections may be inserted to causethe systern to be resonant I at the applied input frequency.

An adjustable tuning stub comprising a length of tubing 25 with acentrally positioned conductor 21, is connected to the resonant sectionin, l I, and provides a means for closely matching the input impedanceof the frequency multiplier to the impedance of the generator or otherinput source of the fundamental frequency. Tuning may be effected eitherby a slidable trombone section embodied in the stub or by a washer 28 ofbrass or other metal which is slidable along the central conductor 21 ofthe stub.

The right hand end of the tube I0 may be open,

instead of closed, and reflection also will occur and standing waves areformed, but in this case a maximum voltage value of the standing wavewill, appear at the open end, and thus the point b would be located at adistance from the end of the tube corresponding to one-half of thefundamental wave, as shown in Fig. 3, so that points a and b willrepresent adjacent crests or maximum voltage values of the standing wavecomponent. Such an arrangement, however, is .not

\ as efiicient as that in which the end of the tube I0 is closed,because some of the energy escapes or is radiated from the open end. i

The frequency multiplier may be employed with a resonant section in atransmission line, in which case a traveling wave, instead of a standingwave, will cause a difference in potential at the points a and I) suchas to induce in the resonant chamber 22 waves which are received by thepickup loop 26a. The standing wave arrangement is preferred, however,because of the higher voltage crests resulting therefrom and hence agreater amount of power obtainable.

While the frequency multiplier is primarily adapted for relatively lowpower because of the current limitations of the .crystal rectifiers, asufiicient output is obtained to provide a very high frequency sourcefor use in connection with wave guides, chambers, and the like, and thehigh frequency source thus obtainedv may, if desired, be amplified bysuitable amplifiers designed to operate at such frequencies. a

It will be apparent from the foregoing that the frequency multiplierunit maybe constructed in various physical forms other than thatspecifically illustrated, and various modifications thereof may beemployed, so long as the system enables suitable balanced voltages toground to be obtained and applied to the resonant chamber 5.;portion forreceiving alternating current standing electromagnetic wave is set up inthe disclosing the principles.

of the invention which is not to be regarded as limited except asindicated by the scope ofthe appended claims.

What is claimed is:

1. A high frequency multiplier system comprising a transmission linestructure having an input portion for receiving a source of highfrequency alternating current whereby an electromagnetic wave is set upin the transmission line structure in response to said input current, atleast two rectifiers having input circuits respectively coupled to saidtransmission line structure at longitudinally spaced placescorresponding to points on said electromagnetic wave that differ inphase whereby a plurality of current pulses of different time phase arepassed by the rectiflers during each cycle of the alternating currentinput to said transmission line structure, a wave chamber which isresonant at a frequency that is a harmonic of the fundamental frequencyof said alternating current input, coupling means connecting the outputcircuits of the rectifiers with said resonant wave chamber includingmeans within the chamber for exciting it by the unidirectional currentpulses received from the rectifiers, and an output circuit includingpickup means in said resonant chamber responsive to the waves set uptherein for producing a source of alternating current having a.fundamental frequency corresponding to the harmonic selected by theresonant chamber.

2. A high frequency multiplier system comprising a coaxial linestructure having an input portion for receiving a source of highfrequency alternating current whereby an electromagnetic wave is set upin the coaxial line structure in response to said input current, atleast two rectifiers having input circuits respectively coupled to saidcoaxial line structure at longitudinally spaced places corresponding topoints, on said cycle of the alternating current input to said coaxialline structure, a wave chamber which is resonant at a frequency that isa harmonic of the fundamental frequency of said alternating having afundamental frequency corresponding to the harmonic selected by theresonant chamber.

3., A high frequency multiplier system comprising a resonant linestructure having an input a. source of high frequency and characterizedin that a resonant line structure in response-to said input current, atleast two rectifiers having input cir'-' cuits respectively coupled tosaid resonant line structure at longitudinally spaced placescorresponding to points on said standing electromagnetic wave thatdiffer in phase whereby a plurality of current pulses of different timephase are a frequency that is a mental frequency of including pickupmeans in said resonant chamber responsive to the waves set up thereinfor producing source of alternating current having a fundamentalfrequency corresponding to the quency alternating passed by therectifiers during each cycle of the alternating current input to theresonant line structure, a wave chamber which is resonant at harmonicselected by the resonant chamber,

4. A high frequency multiplier system comprising a coaxial resonant linestructure having an input portion for receiving a source of highfrecurrent and characterized in that. a, standing electromagnetic waveis set up in the coaxial line structure in response to said inputcurrent, at least two rectifiers having input circuits respectivelycoupled to said wave guide at longitudinally spaced places correspondingto points on said standing electromagnetic wave that are approximatelyopposite in phase whereby at 5. .A- high frequency multiplier systemcomprising a coaxial resonant line structure havingan input portion forreceiving a source of high frequencyalternating current andcharacterized in that a standing electromagnetic wave is set up in inputcurrent, at least put circuits respectively coupled by means of coaxialtube sections to said resonant line structure at longitudinally spacedplaces corresponding-to are'passed by the rectifiers during each cycleof the alternating current input to said resonant line structure, theeffective length of each of said coaxial tube sections correspondingapproximately to the wavelength of a harmonic of the fundamentalfrequency of said alternating current input, a wave chamber which isresonant at the frequencyof said harmonic, coupling means comprisingother coaxial tu'oe sections connecting the outputcircuits of threctifiers with said resonant wave chamber and including means withinthe chamber for exciting it by the unidirectional current pulsesreceived from the rectifiers, andan output circuit includingvpickupmeans in said resonant chamber responsive to the waves set up thereinfor producing a source of alternating current having a fundamentalfrequency corresponding to said harmonic selected by the resonantchamber.

6 A high frequency multiplier system com- I prising a coaxial resonantline structure having an input portion for receiving a source of highwave that are opposite in frequency alternating current andcharacterized in that a standing electromagnetic wave is set up in theresonant line structure in response to said input current, at least tworectiflershaving input circuits respectively coupled to said resonantline structure at longitudinally spaced places corresponding phase andone-half the wavelength of that of said alternating current inputwhereby two current pulses of different time phase are passed by therectifiers durto points on said electromagnetic ing each cycle of thealternating current input to said resonant line structure, a wavechamber which is resonant at the second harmonic of the fundamentalfrequency of said alternating current input, coupling means connectingthe output circuits of the rectifiers with said resonant wave chamberincluding means within the chamber for exciting it by the unidirectionalcurrent pulses received from the rectiflers, and an output circuitincluding pickup means in said resonant chamber responsive to the wavesset up therein for producing a source of alternating current having afundamental frequency corresponding to said second harmonic selected bythe resonant chamber.

7. A high frequency multiplier system comprising a transmission linestructure having an input portion for receiving a source of highfrequency an electromagnetic in the transmission line structure inresponse to said input current, at least two rectiflers having inputcircuits respectively coupled by means of coaxial tube sections to saidline structure at longitudinally spaced places corresponding to pointson said electromagnetic wave that difler in phase whereby at least twocurrent pulses of different time phase are passed by the rectifiersduring each cycle of the alternating current input to said linestructure, the effective length of each of said coaxial tubesectionscorresponding approximately to an odd onehalf wavelength of thefundamental wave of said alternating current input, a wave chamber whichis resonant at a frequency that is a harmonic of the fundamentalfrequency of the alternating current input, coupling means comprisinganother coaxial tube section connecting the output circuits oftherectifiers with said resonant wave including means within the chamberfor exciting it by the unidirectional current rectifiers, the effectivelength of said last named coaxial tube section correspondingapproximately to an odd eighth wave length of said fundamental wave, andan output circuit including pickup means in said resonant chamberresponsive to the waves set up therein for producing a source ofalternating current having a fundamental frequency corresponding to saidharmonic selected by the resonant chamber,

GEORGE E. PIHL.

